Google will be your source. Many local distributors will NOT simply because HVAC is not really DIY. For a gas furnace, a permit is mandatory, and a homeowner can do that in some states, but we are messing with gas here.

For the air conditioning side, a DIY does not have the EPA certificate to purchase and work with R22, and does not have the THOUSANDS of dollars worth of tools....recovery system, vacummp pump, gauge manifold, brazing set, etc. Not to mention the knowledge of how to set your superheat/subcool, etc.

I just found several store fronts on ****. There are probably others as well on the internet. Some local shops will usually work with you. They can size the equipment and make all the duct work then you can install it.

You will probably pay more buying local but you will have support you can not get online. If doing A/C they can braze the joints, pull a vacuum, and get it charged properly.

If you are lucky you might find a local guy with a scratch and dent unit he will sell cheap. Reputable business will not install scratch and dent so somebody that will take them off their hands for some $$$ is a good deal for everybody.